Many of us who are hardware oriented find it hard to walk past a seemingly lonely abandoned consumer electronics product without thinking “if only I could drag it back to the car and take it home”. [phooky] of New York City resistance company is no stranger to this sentiment. An old Epson wf-2540 inkjet printer was disassembled because of its important “nutrients”. You know, these good things are like fashionable motors, encoders and switches. But what do you do with the control panel? After all, they are often very specific to the requirements of the devices they control, and usually do not provide much reuse space.
Rp2040 PIO is fully capable of introducing these LCD pixels
[phooky] I don’t usually worry about them, but I decided to try it this time. Internally, there is nothing different. A large single-sided PCB is used for key switches and LEDs, and a small PCB carries LCD display. The simplest part is to figure out how the keyboard scan is completed. The result is very simple. It only uses the 74 series shift register device to scan the columns and clock out the rows. The raspberry PI Pico module was put into use to scan the keyboard and create a keyboard map with pure brute force. No tracking circuit is required. When [phooky] began to study the LCD interface based on Epson e02a46ea chip, things became interesting (good luck, found the data sheet of the chip!) Soon realized that the document was not available at all, so it was necessary to take a difficult approach. Poke from the line of the main CPU (an Epson e01a9ca, whatever it is), the display clock is recognized, there are some control signals, and three lines of RGB channel. By throwing saleae data capture into some ROM exploration software, the display configuration was determined as standard 320 × Unit 120.
The PIO unit of rp2040 is used to generate video waveform and output pixels to LCD controller, so that the rp2040 board can be permanently connected in the chassis and convert the control panel into USB device for operation!
Want to learn more about reverse engineering garbage (or non garbage) projects and re-use them according to your wishes? Check out this hacker article a few weeks ago. For something more advanced, you can try it at a hacker site of automobile electronic control unit.